1. Field of the Invention
This invention relates to the field of optical communications networks and more particularly to the field of fiber optic components and to micro-actuators made by MEMS (Micro Electro-mechanical Systems) related processes for use in optical switches.
2. Description of Related Art
Optical switches pass optical signals from one optical port to another optical port or serve to interrupt an optical signal in response to an electrical command such as a logic signal. In U.S. Pat. No. 4,932,745 to Blonder, assigned to ATandT, the disclosure of which is incorporated by reference herein in its entirety, an optical switching arrangement has a mirror which is positioned either out of an optical path or in an optical path to deflect optical signals between input and output fibers. The switching arrangement has first, second, third and fourth optical ports which are formed by respective proximate ends of first, second, third and fourth fiber segments disposed in respective grooves etched or otherwise formed in a silicon substrate base. The switching arrangement further comprises first, second, third and fourth lenslets that serve to collimate the respective optical beams emanating from the first fiber, entering into the second fiber, or entering into the third or fourth fibers. The source for these optical beams is supplied by a light source (not shown) and is processed by known optical systems. The mirror has a frontal planar reflecting surface and may also have a rear planar parallel reflecting surface.
U.S. Pat. No. 5,042,889 assigned to ATandT, the disclosure of which is incorporated herein by reference in its entirety, shows another type of optical switch.
The invention is a bi-stable micro-actuator shown in a first alternative embodiment as an optical switch. The actuator has a frame. A flexible transfer member is supported at a first and second point of support. The member has a compressive axis that extends from its first to its second point of support.
An expandable structure is coupled to the frame and has a first and second end coupled to drive the transfer member""s first and second point of support. When assembled, the flexible transfer member is pre-stressed to compress the expandable structure and to hold the flexible transfer member in compression in a bowed state. The flexible transfer member has a central portion displaced in a vertical plane, from the compressive axis. A control signal, having a first state during which no voltage is applied to heater electrodes and a second state during which a pulse of voltage of predetermined amplitude and duration is applied to heater electrodes to heat elements of the expandable structure that expand to reduce the compressive force applied to the flexible transfer member. As the compressive force is relaxed, in response to the control signal assuming a second state, the central portion of the flexible transfer member moves past the compressive axis. As the flexible transfer member moves in response to application of the control signal second state, the control signal returns to a first state after a predetermined interval, the duration of the interval being selected to insure that the central portion of the flexible transfer member passes into a bowed second state from which return to the first state would be possible only by returning the control signal to the second state. The return of the control signal to a first state permits the heater to cool restoring the compressive force applied by the expandable structure to the flexible transfer member.
In another alternative embodiment a first collimated optical signal source is coupled to the frame to provide an optical signal via an optical signal path. A first optical port is coupled to the frame and co-axially aligned with the collimated signal source to receive the optical signal. A transfer member surface is positioned on the central portion of the flexible transfer member. The transfer member surface, such as a vertically disposed mirror surface, is positioned on the flexible transfer member so as to be free of the optical signal path with the flexible transfer member, in compression, and in a bowed first state. The transfer member surface is moved to a position to totally block or reflect the optical signal path with the flexible transfer member in compression in a bowed second state. In this arrangement, the bi-stable micro-actuator functions to provide an optical switch function.